It is increasingly common for surgical procedures to involve navigation or tracking of instruments used during the surgery. Surgical navigation can be helpful in avoiding delicate neural or vascular structures when moving implants or instruments within a patient. In spinal surgery, for example, a surgical navigation system can be used during screw insertion, disc removal, bone preparation, and other steps of the surgery. Use of surgical navigation systems can also reduce the amount of X-ray exposure to which the patient and operating room staff are exposed.
A typical navigation system includes an array of markers attached to a surgical instrument, an imaging system that captures images of the surgical field, and a controller that detects the markers in the captured images and tracks movement of the markers within the surgical field. The controller associates a reference frame of the imaging system with a reference frame of the patient and, informed by a known geometry of the array and the instrument, determines how the instrument is being moved relative to the patient. Based on that determination, the controller provides navigation feedback to the surgeon.
The precision of the navigation system is strongly dependent on the design of the navigated instrument. When the navigation array is welded to the instrument or integrally-formed with the instrument, relatively high precision can be achieved. Such arrangements can be inconvenient, however, as the capability to remove the array from the instrument or to attach the array to other instruments is lacking. Further, arrangements having the navigation array integrally-formed with the instrument can require separate instruments for standard and navigation use, thereby raising costs for equipment.
A number of modular systems have been developed to allow the navigation array to be interchangeably attached with one or more instruments. These systems can be cumbersome to use, often requiring two hands, numerous steps, and/or additional tools to attach the array to the instrument and to remove the array from the instrument. These systems can also allow for considerable “play” between the instrument and the array, which can undesirably reduce the precision of the navigation. For example, toggling of the instrument relative to the array can introduce navigation error. Also, navigation error can be introduced if the array is not consistently attached to the instrument at a known or predetermined location and/or orientation.